The present invention relates to apparatus and system for determining the integrity of sealed containers. The invention relates more specifically to a novel gimbal-type anvil for systems and devices of this type.
The broad field of the invention has application to parenteral pharmaceutical products which are typically packaged in rigid glass containers sealed with a combination rubber and metal closure. These products are usually packaged on high speed automatic filling and capping equipment. Specifically the containers are filled with a medicament at a filling station and thereafter the closure assembly consisting generally of a resilient sealing element made of rubber and a cup-like cap made of aluminum is placed over the discharge end of the container. The capping apparatus then acts to apply a predetermined force to the cap to seat the closure and to crimp the lower edge of the skirt of the cap under or around the bottle finish or flange to seal the container. In this capping operation, the resilient sealing element is compressed between the end face of the container and the cap and held in a compressed state by crimping the cap to the container. The integrity and adequacy of the seal, therefore, is primarily a function of the percent compression of the sealing element or expressed another way, the magnitude of the sealing force of the seal against the container around the periphery of the opening in the container. Proper sealing for medicaments is important to prevent exposure to air or loss by evaporation and also to protect the contents from microbiological or other contamination.
It has been found that some containers packaged in this way are not adequately sealed. Hence, it is desirable to provide means for checking the adequacy of the seal and rejecting those containers which are not properly sealed. Apparatus and system for checking seal integrity for this purpose is shown and described in a pending application in the name of L. David Leiter and Jacob Ravn owned by The West Company, assignee of the present application, entitled APPARATUS, METHOD AND SYSTEM FOR DETERMINING THE INTEGRITY OF SEALED CONTAINERS filed May 12, 1980 and bearing Ser. No. 148,694 which issued as U.S. Pat. No. 4,315,327 on Feb. 16, 1982. This application is incorporated herein by reference. Recapping briefly the operation of the system disclosed therein, the apparatus includes means for applying a gradually increasing external force to the metal cap of the sealed container-closure assembly which at some point will equal and then exceed the residual static force in the resilient sealing element. External force is applied to a localized area of the cap along a circumferential line adjacent the juncture of the top and skirt in the zone of maximum compression of the resilient sealing element by an anvil. When this force threshold is crossed, the metal outer cap will begin to move downward as the resilient sealing element is further compressed slightly by the additional load from the applied force. The system further includes means for detecting the initial downward movement of the metal cap and observing the value of the force applied at that instant which essentially equals the residual static force in the resilient sealing element. Then, if the residual static force exceeds a predetermined minimum force to provide an adequate seal as determined empirically for a given container-closure assembly, the seal is satisfactory and if below the acceptable minimum, then, of course, the seal is of inadequate integrity and the container-closure assembly is rejected. The type of anvil illustrated in the Leiter et al application, Ser. No. 148,694, comprises a stem and an anvil head which may be assembled to the actuator arm or shaft of the force applicator unit by a simple threading of the stem to a threaded stud at the lower terminal end of the actuator shaft. The lower end of the stem is a universal fitting which has a pocket for mounting a ball defining a pivot point located on the longitudinal axis of the container-closure assembly and spaced upwardly from the feeler wall defined in the anvil head which engages the peripheral edge of the cap along a circular line approximately at the vertical center line of its corner radius. This anvil is primarily for use with closures which have a flat top since the wall portion of the anvil head overlies and is spaced closely to the top when the feeler wall engages the outer peripheral portion thereof along the circular line L. Thus, the anvil is not suited for closures of the type illustrated herein which have a projection extending upwardly from the top of the cap. Moreover, it has been found that when the anvil is used on small-sized closures it has a tendency to cock and transmit a lateral force to the cap since the pivot point is located above the plane of the feeler wall which engages the top of the cap. This produces inaccurate force readings and may result in accepting container-closures which are in fact inadequately sealed.
The present invention provides a novel gimbal-type anvil for use in seal integrity checking systems of the general type described above and is characterized by novel features of construction and arrangement so that closures having projections or the like can be accommodated. Furthermore, the pivotal arrangement of the cooperating ring members forming part of the anvil acts in a way to produce levelling because of a more optimum location of the pivot point relative to the plane of the feeler wall which engages the cap thus eliminating the tendency to cock which produces lateral forces which in turn may produce inaccurate force readings. More specifically, the gimbal-type anvil of the present invention is a two axis gimbal anvil which essentially distributes the force applied to the sealed container more evenly on the cap minimizing the tendency of the cap to tilt when the external force is applied and thereby produce inaccurate readings.
Accordingly, it is an object of the present invention to provide a new and useful two-axis gimbal-type anvil for use in apparatus and system for checking seal integrity of sealed containers which distributes the applied force more evenly to the cap element of the closure so that the force readings may be checked more accurately.
Another object is to provide an anvil which is of comparatively simplified design and is easy and economical to manufacture.
A still further object of the present invention is to provide an anvil which is not only useful with a specialized closure assembly for containers but may also be effectively used to provide accurate readings on a variety of closure elements for containers.
Still another object of the present invention is to provide a gimbal-type anvil for apparatus and system for checking seal integrity which minimizes the chance of error even when utilized by operators with minimal skills.